1. Field of the Invention
This invention relates in general to off-road endless track type vehicles, also called bulldozers or crawler tractors. More particularly, the invention relates to counterweight attachments for crawler tractors for use where the vehicle is operated on steep slopes or grades.
2. Background Art
Conventional crawler tractors have dozer blades at the front which are employed for such jobs as dozing and moving or scraping earth, boulders, tree stumps and the like. A number of different attachments can be provided for specialized work. One such attachment is a side-mounted boom structure for laying pipe. Another prior art attachment for a tractor type vehicle is a side-mounted hoisting boom. Another common crawler tractor attachment is a rear-mounted ripper blade which can be used for such purposes as tearing up concrete or asphalt pavement or compacted earth.
Off-road vehicles have previously been provided with counterweights for various purposes. The relevant prior art includes U.S. Pat. No. 4,279,348 which provides a counterweight that swings to one side of a crawler vehicle for balancing a pipe laying boom assembly. U.S. Pat. No. 2,261,870 provides another side-mounted counterweight for use with hoisting machinery on a crawler tractor. U.S. Pat. No. 4,299,530 provides a fore and aft shifting counterweight device on a wheeled front end loader which has a backhoe. U.S. Pat. No. 4,502,709 provides a lateral shifting counterweight which operates when the frames of an articulated vehicle pivot. U.S. Pat. No. 4,861,069 provides an arrangement for a four-wheeled tractor in which a counterweight shifts left or right when the vehicle is on a lateral slope. U.S. Pat. No. 1,852,200 provides a road scraper in which a fixed counterweight is provided at the rear to balance a load at the front.
The prior art counterweight devices that have heretofore been provided do not effectively address the problems encountered when a crawler tractor uses its blade to scrape or push on a steep grade or slope. For example, in dozing operations where the tractor backs up a steep slope, the tractor center of gravity is displaced forward of the tracks from the position it would normally occupy when on level ground. This results in a loss of traction which reduces dozing efficiency.